JPH0727844B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid electrolytic capacitor with good performance using lead dioxide as a semiconductor.

2. Description of the Related Art A solid electrolytic capacitor using lead dioxide as a semiconductor layer is known as described in, for example, Japanese Patent Publication No. 58-21414. However, in the above-mentioned conventional solid electrolytic capacitor, since the method of forming lead dioxide on the oxide film is a method of thermally decomposing the reaction mother liquor containing lead ions, the oxide film may be thermally cracked. Further, there is a problem that the generated gas causes chemical damage. Therefore, when a voltage is applied to this solid electrolytic capacitor, current may concentrate on the defective portion of the oxide film, causing dielectric breakdown. Therefore, in order to increase the reliability of the withstand voltage, the formation voltage must be 3 to 5 times the rated voltage, and in order to obtain a predetermined capacity, a large anode body having a large surface area must be used. There is a problem that there is no.

Further, as described in JP-B-49-29374, a method of forming lead dioxide on an oxide film by chemical deposition is known. However, this method requires silver ions as a catalyst for chemically precipitating lead dioxide, so that silver or a compound of silver is attached to the derivative oxide film, resulting in a decrease in insulation resistance. .

Problems to be Solved by the Invention An object of the present invention is to provide a semiconductor layer of lead dioxide on an oxide film tan δ without utilizing a thermal decomposition reaction and without using a catalyst that adversely affects the capacitor performance. (Induction tangent)
Another object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor having a small leakage current.

Means for Solving the Problems As a result of various studies to solve the above-mentioned drawbacks of the prior art, the present inventors have found that a reaction mother liquor containing a lead-containing compound and hydrogen peroxide and / or a chloric acid calcium compound, By forming a semiconductor layer of lead dioxide on the oxide film by chemical deposition, the above-mentioned object is achieved very effectively,
It was found that a solid electrolytic capacitor with good performance was obtained, and the present invention was completed.

That is, according to the method of the present invention, a solid is characterized in that the semiconductor layer is lead dioxide chemically precipitated from a reaction mother liquor containing a lead-containing compound and hydrogen peroxide and / or a calcium chlorate compound. An electrolytic capacitor is provided.

The oxide film in the present invention is an oxide film of a valve metal such as aluminum, tantalum, niobium, etc., a wire, or a sintered body, which is known in the art, and can be obtained by a known method.

The solid electrolytic capacitor manufactured by the method of the present invention,
It has a structure in which a part of the lead dioxide semiconductor layer has entered the pores of the valve metal foil, wire or oxide film of the sintered body.

As a reaction mother liquor for forming a lead dioxide semiconductor layer on the oxide film by chemical deposition, a solution containing a lead-containing compound and hydrogen peroxide and / or a chloric acid-based calcium compound is used.

The solvent used for adjusting the reaction mother liquor may be any one as long as it dissolves the lead-containing compound and the hydrogen peroxide and / or calcium chlorate compound, and is generally water or an organic solvent miscible with water. Is used.

As typical examples of the lead-containing compound used in the present invention, for example, a lead atom is contained in a chelate-forming compound such as oxine, acetylacetone, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds, and cryptate compounds. Lead-containing compounds with coordinate bond or ionic bond, lead citrate, lead acetate, basic lead acetate, lead borofluoride, lead acetate hydrate, lead nitrate, lead chloride, lead bromide, lead perchlorate, Examples include lead chlorate, lead sulfamate, lead hexafluoride, and lead bromate. These lead-containing compounds are appropriately selected depending on the solvent used. Moreover, you may use these lead-containing compounds in mixture of 2 or more types. The concentration of the lead-containing compound in the reaction mother liquor is preferably within the range of 0.05 mol / l from the concentration that gives a saturated solution. If the concentration of the lead-containing compound in the reaction mother liquor is less than 0.05 mol / l, a solid electrolytic capacitor with good performance cannot be obtained, and if the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturation solubility, the amount is increased. No merit of addition is recognized.

Typical examples of the chloric acid-based calcium compound used in the present invention include calcium hypochlorite, calcium chlorite, calcium chlorate, calcium perchlorate and the like. These chloric acid-based calcium compounds are appropriately selected depending on the solvent used. Moreover, you may use these chloric acid type calcium compounds in mixture of 2 or more types.

The amount of hydrogen peroxide or chloric acid-based calcium compound used is preferably in the range of 5 to 0.05 times the molar amount of the lead-containing compound used. If the amount of hydrogen peroxide or calcium chlorate compound used is more than 5 times by mole, there is no cost advantage, and if it is less than 0.05 times by mole, a solid electrolytic capacitor with good performance cannot be obtained. .

As a method for forming a lead dioxide conductor layer on an oxide film, for example, a solution containing a lead-containing compound and a solution containing hydrogen peroxide and / or a calcium chlorate-based compound are mixed to prepare a reaction mother liquor. Then, the reaction mother liquor is applied to the oxide film to chemically deposit it.

The solid electrolytic capacitor manufactured by the method of the present invention,
It has the following advantages over the conventionally known solid electrolytic capacitors.

Since the lead dioxide conductor layer can be formed on the oxide film layer without heating to a high temperature, there is no risk of damaging the oxide film of the anode, and there is no need to perform anodic oxidation (reformation) for repair.

As a result, the rated voltage can be increased several times that of conventional products.
In order to obtain a capacitor having the same capacity and the same rated voltage, the shape can be made smaller than the conventional one.

 Small leakage current.

 A high breakdown voltage capacitor can be manufactured.

Since the electric conductivity of the conductor layer is sufficiently high as 10 ^-1 to 10 ^-1 s · cm ^-1 , the impedance is low.

 tanδ is small.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The characteristic values of the solid electrolytic capacitors of each example are shown in the table.

Example 1 An aluminum foil (purity: 99.99%) having a thickness of 100 μm was used as an anode, and the surface of the foil was electrochemically etched by a direct current to have an average pore diameter of 2 μm and a specific surface area of 12 cm ² / g. This etched aluminum foil was electrochemically treated in a solution of boric acid and ammonium borate to form a thin layer of the derivative on the aluminum foil.

Next, the aluminum foil provided with the above dielectric layer was immersed in a 2 mol / l aqueous solution of lead acetate trihydrate, and 1.2 times mol of hydrogen peroxide solution was added to the lead acetate trihydrate. After standing for 2 hours, the produced lead dioxide layer was thoroughly washed with water to remove unreacted substances and by-products, and then dried at 120 ° C. for 2 hours. Next, a carbon paste was applied on the lead dioxide layer and dried, and then a silver paste was applied on the carbon paste and dried again. A copper wire was used for the cathode, and the resin was sealed to produce a solid electrolytic capacitor.

Example 2 A solid was prepared in the same manner as in Example 1 except that a saturated ethyl alcohol solution of lead acetylacetone synthesized from lead chloride and acetylacetone according to a conventional method was used in place of the aqueous solution of lead acetate trihydrate in Example 1. An electrolytic capacitor was produced.

Example 3 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that an aqueous solution of lead nitrate was used instead of the aqueous solution of lead acetate trihydrate.

Example 4 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that a saturated aqueous solution of calcium chlorate was used instead of the hydrogen peroxide solution.

Example 5 In Example 1, hydrogen peroxide solution was added to lead acetate trihydrate in an amount of 0.
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the amount of 2-fold mole was added, and that the amount of calcium chlorate was added 0.2-fold mole relative to lead acetate trihydrate.

Comparative Example 1 In an aluminum foil having a dielectric layer similar to that of Example 1,
A lead dioxide layer was formed by a conventionally known thermal decomposition method of an aqueous solution of lead nitrate. After repeating this operation four times, a carbon paste layer and a silver paste layer were provided in the same manner as in Example 1 to prepare a solid electrolytic capacitor.

Claims (1)

[Claims] 1. A lead dioxide layer is chemically deposited as a semiconductor layer on the oxide film from a reaction mother liquor containing a lead-containing compound and hydrogen peroxide and / or a calcium chlorate compound. Manufacturing method of solid electrolytic capacitor.